[PATCH 0/5] Remove struct main_type.vptr_{fieldno,basetype}

[Doug Evans <xdje42@gmail.com>]

Hi.

Anytime you can reduce the size of struct main_type that's A Good Thing.
Alas in this case my motivation, besides more general cleanup (will it
never end?), is that I may wish to add something to struct main_type.
Now I can, if I need to.

There are two fields in struct main_type that really shouldn't be there:
vptr_fieldno, and vptr_basetype.  Every type has to pay the price
in memory usage for their presence.  The proper place for them is
in the type_specific field (in this case cplus_stuff) which exists
for this purpose.

Things are a bit complicated because vptr_basetype is overloaded
to record the type of "this" for TYPE_CODE_{METHODPTR,MEMBERPTR,METHOD},
and is accessed through the macro TYPE_DOMAIN_TYPE.

There is also the wrinkle, discussed earlier, that m2-typeprint.c
uses TYPE_DOMAIN_TYPE.  I've replaced that with TYPE_TARGET_TYPE
and left a FIXME there (pre-discussed with Gaius).  This is done in 4/5.

The series has been tested on amd64-linux with dwarf and stabs.
It needs more testing, eg., on other file formats (e.g., xcoff).
And it could use another set of eyes.

One thing I did was rename TYPE_DOMAIN_TYPE to TYPE_SELF_TYPE.
My mind is far too used to associating the word "domain" with
VAR_DOMAIN, STRUCT_DOMAIN, etc.  A better name would be nice.
I went with "self" because TYPE_THIS_TYPE was a bit confusing.
Another alternative is TYPE_TYPE_OF_THIS, but TYPE_SELF_TYPE
"works for me".  Internally, some of the debug info readers
still use "domain", which is fine by me, and I've left those alone.

1/5 - Finish TYPE_SPECIFIC_FIELD handling in copy_type_recursive
2/5 - Tighten up handling of types passed in gnu-v3-abi.c
      ["info vtbl my_int" will currently call INIT_CPLUS_SPECIFIC on that int!]
3/5 - Rename TYPE_DOMAIN_TYPE to TYPE_SELF_TYPE
4/5 - Create TYPE_SPECIFIC_SELF_TYPE and have TYPE_CODE_{METHODPTR,
      MEMBERPTR,METHOD} use it.
5/5 - Finally, move vptr_fieldno,vptr_basetype into cplus_struct_type.